This invention relates generally to transmission and transaxle casings and, more particularly, relates to a fastener less, hydrostatic transmission or transaxle casing.
Transmission and transaxle casings of conventional construction are well known in the art. An example of one such transaxle casing is disclosed in U.S. Pat. No. 5,330,394 to Hauser et al. entitled "Rider Transaxle Having Improved Casing Design." As illustrated by the '394 patent, known transmission and transaxle casings are typically formed by fastening two or more casing components together. More specifically, the casing components are formed with complimentary fastener accepting apertures through which a fastener, such as a bolt or the like, is passed to secure the components in mating engagement.
A further transaxle casing may be seen in U.S. Pat. No. 5,613,409 to Hauser entitled "Axle Driving Apparatus Having Improved Casing Design." In particular, the '409 patent discloses an integrated hydrostatic transaxle ("IHT") having a casing component to which is fastened a cap plate and an axle cap. As with the '394 patent, the casing components are all formed from a metal, such as aluminum, and provided with fastener accepting apertures through which fasteners are passed to secure the casing components in mating engagement.
While the transmission and transaxle casings found in the prior art work well for their intended purpose, such casings are known to have several disadvantages. In particular, forming the casing components with fastener accepting apertures is seen to be a costly process which requires relatively tight manufacturing tolerances, for example, to ensure the proper alignment of the apertures. Furthermore, the process of using fasteners to couple the various casing components is seen to slow and complicate the assembly process resulting in an undesirable increase in the overall cost of manufacture. Additionally, deflection of the casing components of hydrostatic transmissions and transaxles along the junction surfaces will occur in those areas not directly secured with fasteners (those areas between the fasteners) which may result in the leakage of hydraulic fluid therefrom. Such fluid leakage resulting from the noted intermittent attachment between the casing components may impair the operability of the device and is cosmetically and ecologically unappealing.
From the foregoing, it is seen that a need exists for an improved transmission and transaxle casing.